excillent first instalment, question?

Extremely entertaining, however, I suggest you look up on Wikipedia the story of the "Sinking of the Laconia". This goes into detail on the subject, and it's a dramatic license of the story rather than the whole truth as known by documentary evidence.

Still, a needed spotlight on a relatively little known (today) incident of WW2. Well done Mr Bleasdale!

I read that they built a model of the uboat's insides in South Africa,
where they also filmed it...

I guess they did the same as Das Boot, i.e. built a mock up that could motor along itself. The interior sets were a little too spacious for reality, guess it made filming easier.